1. Field of the Invention
The present invention relates to a conjugate in which a non-peptidyl polymer linker and an immunoglobulin constant region are specifically linked to an amino acid residue of the insulin beta chain excluding the N-terminus thereof via a covalent bond, and a preparation method thereof.
2. Description of the Related Art
insulin is a peptide secreted from the beta cells of the human pancreas as a material which plays a very important role in controlling the blood glucose level in the body. In cases where insulin is not properly secreted or insulin as secreted does not properly act in the body, blood glucose in the body cannot be controlled and is increased, thereby inducing the state referred to as diabetes. The case as stated above is referred to as type 2 diabetes mellitus, and the case where insulin is not secreted from the pancreas to increase blood glucose is referred to as type 1 diabetes mellitus. Type 2 diabetes mellitus is treated with an oral hypoglycemic agent including a chemical material as the main component, and in certain patients, is also treated with insulin. On the other hand, treatment of type 1 diabetes mellitus necessarily requires the administration of insulin.
The insulin therapy as widely used at the present time is a method of administering insulin via injection before and after meals. However, such insulin therapy requires that it be constantly administered three times daily, and therefore causes much suffering and inconvenience in patients. In order to overcome such problems, various attempts have been made. One of them was an attempt to deliver peptide drugs into the body by way of inhalation through oral or nasal cavities by increasing the biological membrane permeability of peptide drugs. However, such a method shows a significantly low efficiency of peptide delivery in the body compared to injection. Accordingly, there are still many difficulties in maintaining the in vivo activity of peptide drugs in the required conditions.
Further, a method for delaying absorption after subcutaneous administration of excessive drugs has been attempted. According to this, a method for maintaining blood drug concentration through only a single administration daily has been presented. Some have been approved as medicinal products (e.g. Lantus, Sanofi-aventis) and are currently administered to patients. The study to modify insulin with fatty acids to strengthen the binding of an insulin polymer and to extend the duration through binding to albumin present at the site of administration and in blood has progressed, and drugs produced using such a method have been approved as medicinal products (Levemir, NovoNordisk). However, such methods have the side effect of causing pain at the site of administration, and additionally, the administration interval of a single injection daily still causes significant inconvenience for patients.
Meanwhile, it was reported that the N- or C-terminal region, i.e. the amino acid residue at the position 29 of the insulin beta chain, does not significantly influence binding of insulin to the insulin receptor (Jens Brange and Aage Volund, Adv. Drug Deliv. Rev., 35(2-3): 307-335 (1999); Peter Kurtzhals et al., Diabetes, 49(6): 999-1005 (2000)).
Accordingly, the present inventors have studied to develop a method of modifying an amino acid residue at the C-terminal region of the insulin beta chain with a non-peptidyl polymer and an immunoglobulin constant region, and they found that this method is used to prepare a conjugate having higher binding affinity to the insulin receptor than conjugates prepared by modifying other sites of insulin such as a N-terminus, thereby completing the present invention.